Turbo charged engines utilize a Charge Air Cooler (CAC) to cool compressed air from the turbocharger, before it enters the engine. CACs may either use cooled coolant passing through the CAC or ambient air passing across the CAC to cool charge air passing through the inside of the CAC. As such, a CAC coolant pump or CAC fan, coupled to the CAC, may control local CAC cooling. Grille shutters positioned at a vehicle front end and an engine cooling fan may control a flow of ambient air from outside the vehicle to the CAC, thereby controlling external CAC cooling. The manifold charge air temperature, or temperature of the air exiting the CAC, may be controlled by adjusting local and external CAC cooling. CACs may be used to maintain the charge air at a temperature low enough to increase combustion stability but high enough to reduced condensate formation within the CAC. However, in some cases, CACs may be slow to respond to temperature fluctuations and increase, rather than decrease, downstream charge air temperatures.
Other attempts to address maintaining a target charge air temperature include adjusting a CAC coolant pump (e.g., on/off), grille shutters, and/or engine cooling fan in response to a measured manifold charge air temperature (e.g., CAC outlet air temperature). For example, in response to a manifold charge air temperature increasing above a target value, a coolant pump may be turned on to decrease the temperature of the charge air exiting the CAC.
However, the inventors herein have recognized potential issues with such systems. As one example, adjusting the above cooling devices in response to a measured manifold charge air temperature alone may result in decreased precision in maintaining a target manifold charge air temperature. For example, if ambient air temperature increases or decreases, this type of control may not adjust the cooling devices until the manifold charge air temperature moves away from the target temperature. As such, condensate formation or combustion instability may increase.
As one example, the issues described above may be addressed by a method for adjusting a charge air cooler fan or charge air cooler coolant pump and an engine cooling fan and/or vehicle grille shutters based on a target manifold charge air temperature and additional air and coolant temperatures. The additional air and coolant temperatures may include ambient air temperature, CAC coolant temperature, and CAC inlet air temperature.
In one example, one or more of a grille shutter position and an engine cooling fan speed may be adjusted based on a difference between a target manifold charge air temperature and a charge air cooler inlet coolant temperature. The adjustments to the grille shutters and engine cooling fan may be further based on ambient temperature. Additionally, a coolant pump output, such as coolant pump speed, may be adjusted based on a difference between a charge air cooler inlet air temperature and the target charge air cooler air temperature. Adjustments to the coolant pump speed may be further based on a mass air flow rate, a difference between a target coolant temperature and a charge air cooler inlet coolant temperature (e.g., CAC cooling capacity), and a difference between a measured manifold charge air temperature and the target manifold charge air temperature. Using this method, the pump and engine cooling fan may be run only when required based on the above temperature values. As such, controlling the manifold charge air temperature in this way may increase engine operating efficiency and reduce wear on cooling system components while increasing the accuracy and precision of maintaining the target manifold charge air temperature.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.